Various relatively small motorized vehicles, such as snowmobiles and golf carts, use a V-belt type continuously variable transmission. Variable transmissions include a drive pulley or clutch and a driven pulley or clutch. Each pulley is composed of a fixed sheave or pulley half that is fixed in the axial direction, and a movable sheave or pulley half, which is movable in the axial direction. A V-belt joins the drive pulley and the driven pulley.
These variable transmissions are equipped with a speed or revolution per minute (RPM) responsive mechanism associated with the drive pulley and a torque responsive mechanism associated with the driven pulley. Therefore, the drive pulley and the driven pulley continuously vary the shift ratio in relation to the drive speed and the driven torque.
When the torque load upon the driven shaft is increased with the increase in the load upon the drive track, as when the vehicle runs uphill, the torque responsive mechanism transmits an axial force matching that increase from the driven pulley to the drive pulley so that a satisfactory shift ratio can always be attained.
The torque responsive mechanism can include inclined cam surfaces which are opposed to one another and positioned between a helix, sometimes referred to as a spring cap, which is fixed to the movable sheave-half or pulley-half, and a fixed sheave half or pulley half. Those opposed inclined cam surfaces move in the axial direction relative to each other by the torque loaded upon the driven shaft, while the pulley halves are sliding and turning relative to each other. The movable sheave is moved relative to the fixed sheave by the relative movement caused by the cooperating cam surfaces. The effective diameter of the driven pulley is increased by moving the two pulley halves closer together.
A spring interposed between the fixed sheave and the spring cap provides a preload conditional thereby creating a maximum diameter. The spring is both in compression and in torsion. In order to adjust the preload, the driven pulley needs to be taken apart and the connection points of the springs adjusted.